1. Field of the Invention
This invention relates to impact-absorbing packaging devices, and more particularly, to containers employing yieldable packing material to protect fragile articles from damage by impact during shipping and storage.
2. Prior Art
Prior art impact-absorbing packaging devices for shipping and storing fragile articles fall into four broad categories: In one type of device, the articles are loosely enclosed in a flexible envelope the walls of which are padded with laminated pulverized paper, plastic air bubbles, foam, or similar resilient material. In another, the articles are enclosed in a rigid container and surrounded by a loose fill of impact-absorbing material, such as small pieces of polystyrene foam, shredded newspaper, excelsior, sawdust, or the like, which is intended to cushion them from shock. In a third type, shock-absorbing rigid inserts, such as die-cut paperboard, or wooden or plastic forms, or flexible inserts, such as cushioning sacks containing resilient synthetic plastic foam, support the articles in a rigid container. In a fourth type, the articles are encapsulated in a molded form-fitting shell of crushable material, such as polystyrene foam, which is generally enclosed in a rigid container.
My U.S. Pat. No. 4,193,499, issued Mar. 18, 1980, contains examples of each of these types of packaging systems and a discussion of their respective advantages and limitations. As pointed out there, by reason of those limitations none of the prior art systems satisfactorily fills the need for a convenient effective self-contained impact-absorbing shipping or storage device suitable for low-volume packaging operations or the occasional industrial packaging task.
The invention disclosed in U.S. Pat. No. 4,193,499 is specifically intended to satisfy this need. It comprises a prefabricated double-walled envelope in which expandable material enclosed in the space between the walls is caused to expand, thereby converting the device into an impact-absorbing pod closely conforming to articles sealed in it. In one embodiment of the invention the protective pod is formed by exposing a mixture incorporating polystyrene beads and a blowing agent to microwave radiation. The subject invention offers an alternative method and means for achieving substantially the same result.